Final answer:
The spinal cord originates from the base of the brain and extends to the upper lumbar vertebral bones. Spinal nerves emerge from specific levels of the spinal cord, corresponding to the vertebral column regions.
Step-by-step explanation:
The Spinal Cord and Spinal Nerves
The spinal cord originates from the base of the brain and runs down through the vertebral column. The spinal cord is divided into regions corresponding to the vertebral column: cervical, thoracic, lumbar, and sacral regions. The spinal cord itself does not extend the full length of the vertebral column, ending around the level of the upper lumbar vertebrae, which is why the sacral spinal cord is at the level of the upper lumbar vertebral bones. The cauda equina, a bundle of nerves resembling a horse's tail, extends from the terminated spinal cord. There are 31 pairs of spinal nerves, and each spinal nerve emerges from the spinal cord at a specific level, passing through the intervertebral foramina.
The spinal cord contains major tracts such as the dorsal column system and the spinothalamic tract, originating from sensory neurons in the dorsal root ganglia. The dorsal column system carries information about touch and proprioception, while the spinothalamic tract carries information about pain and temperature sensation. These tracts decussate at different levels in the spinal cord and medulla, thereby connecting with the appropriate sensory or motor pathways in the brain.